Color separation in bifocal lenses???

**Whidbeyeyes** · 07-13-2009, 07:13 PM

Hello!

I recently had a patient initially order polycarbonate st-28 lenses with anti-reflective. She stated that only in her reading area, she was experiencing a color separation with magenta and yellow at the top and black and sienna at the bottom. She compared it to when a register goes out and you can see the color separation.

We thought she might be sensitive to the "interference fringing" which is a result of the hard coating and material. It can cause a "zebra" like striping on the anti-reflective but shouldn't cause any visual problems. Thinking that this patient may just be very sensitive to that, we re-made her lenses into 1.60 high index with anti-reflective.

She is still getting this color separation but only in her reading area which seems very odd. Does any one have any idea on what could be the problem?

**For-Life** · 07-13-2009, 07:17 PM

probably abbe value. Try a cheap pair, without AR in CR-39. if that works, then you have your problem. Then you can make them up in another thin material with AR.

**chip anderson** · 07-13-2009, 08:21 PM

Remember the little rule many members have claimed to be cardinal: "Don't use poly on powers over five diopters." If you had a distance power of four diopters and an add of 2.50 you will noter that the total add power exceeds this by 1.50. More chromatic aberration in add.

Chip

**gmanlook** · 07-14-2009, 10:24 AM

Lots of chromatic abberation in Poly. I would remake them in trivex..has a high abbe value and negligible abberation.

**EyeFitWell** · 07-14-2009, 12:06 PM

But the origional poster says they've already remade them in 1.60.

**DragonLensmanWV** · 07-14-2009, 12:09 PM

Is she a high minus with a deep B measurement frame?
Granted, the change to 1.60 should have eliminated most if not all of the color dispersal, but if she has a long way to go from the center of the frame to the reading area, this can still be a problem.

**CLANDGH** · 07-14-2009, 01:15 PM

Are the lens edges polished? If so that sometimes causes color aberations, especially if you rolled the edge too. The color distortion from polishing may sometimes be noticed by the clients only in the strongest portion of the lens. You may need to dull them back down, edge coat them, or use one of the older AR treatments that can be applied after the lenses are cut. Is she new to wearing bifocals, and so maybe hyper-critical to all the new things she must get used to? Was she a convert from a glass fused bifocal? Did her near RX change much in this pair of glasses? If so, the increase in Add would have resulted in a steeper ledge for light to reflect down through. You can check to see if the ledge is the problem by using one of your black markers (that you use to dot the lens out for check out), blacken the ledge. See if she still sees the color breakdown. If the ledge is the problem, you may have to consider using a different style seg. Your material choice will limit your seg choice. Sometimes a curve top seg solves the problem, a round or blended seg or progressive usually will. The 360 progressive lens designs work well to convert a patient to progressives, Varilux has a progressive lens called "Liberty" that was specifically created to help convert patients from FT. You might also explain to her that many of the best AR treatments are not available on FT because the treatments are thicker and leave a "run-off" by the ledge.

**Fezz** · 07-14-2009, 01:47 PM

Originally Posted by CLANDGH

Varilux has a progressive lens called "Liberty" that was specifically created to help convert patients from FT.

I am of the understanding that the Liberty has been phased out.

**MarcE** · 07-14-2009, 01:49 PM

I bet she is a high plus, like Chip alluded to.
Probably the lenses have polished edges since they normally just come on poly.

I am a bit surprised that 1.60 didn't fix the issue. Is she a previous CL wearer?

CR-39 w/out a polish would be my solution. Fit the BF up tight.

**CLANDGH** · 07-14-2009, 01:57 PM

I'm sure Liberty will be phased out at some point Fezz, but it is in my February pricelist from Essilor, and what do you know, it had a price increase!

**Fezz** · 07-14-2009, 02:02 PM

Originally Posted by CLANDGH

I'm sure Liberty will be phased out at some point Fezz, but it is in my February pricelist from Essilor, and what do you know, it had a price increase!

Interesting.

http://www.varilux.com/en/Products

**Confirmed with a ring to Essilor= Varilux Liberty is no longer available.**

**carnzo** · 07-14-2009, 08:49 PM

Shame on you for using poly, leave that to Lenscrafters/Pearle. This person needs Trivex material w/Super High Vision (AR). Hoya's hardcoat is the same index as the material therefore no zebra reflections. Also, do not use polished edges.